1. Field of the Invention
The present invention relates to information processing apparatuses and methods, information recording media, and computer programs. More particularly, the invention relates to an information processing apparatus and method, an information recording medium, and a computer program that implement strict usage control for content stored in an information recording medium, such as a digital versatile disc (DVD) and content stored in a local storage, such as a hard disk, when the two types of content are simultaneously played back.
2. Description of the Related Art
Various software data (hereinafter referred to as “content”), such as audio data, e.g., music, image data, e.g., movies, game programs, and various application programs, can be stored on recording media, for example, Blu-ray Discs™ using blue laser light, digital versatile discs (DVDs), mini discs (MDs), compact discs (CDs), as digital data. In particular, Blu-ray discs using blue laser light are high-density recording discs and can record a large volume of video content as high-quality image data.
Digital content is stored in various information recording media, such as those described above, and is provided to users. A user uses the digital content by playing it back on a user's personal computer (PC) or player, such as a disc player.
Generally, the distribution rights of many content data, such as music data and image data, are owned by creators or sellers of such content data. Basically, therefore, certain usage restrictions are imposed when distributing content, that is, the use of content is allowed only for authorized users, thereby preventing unauthorized copying.
According to digital recording apparatuses and recording media, images and sound can be repeatedly recorded and played back without a loss in quality. Thus, the distribution of illegally copied content via the Internet, the circulation of recording media, such as compact disc recordable (CD-R) discs, recording copied content thereon, so-called “pirated discs”, the use of copied content stored in hard disks of, for example, PCs, are widespread.
DVDs or large-capacity recording media, such as those using blue laser light which have recently been developed, can record a large volume of data, for example, up to several movies, on one medium, as digital information. Since video information can be recorded as digital information as described above, it is becoming important to perform copyright protection by preventing unauthorized copying. Nowadays, to prevent unauthorized copying of digital data, various techniques for preventing unauthorized copying are practically applied to digital recording apparatuses or recording media.
For example, in DVD players, a content scrambling system is employed. According to the content scrambling system, data, such as, video data or sound data, is encrypted and recorded on, for example, a digital versatile disc read only memory (DVD-ROM), and a key for decrypting the encrypted data is supplied to licensed DVD players. A license is given to DVD players that are designed in compliance with predetermined operation rules, for example, agreeing not to perform unauthorized copying. Accordingly, licensed DVD players can decrypt data recorded on a DVD-ROM by using the given key to play back images or sound from the DVD-ROM.
On the other hand, unlicensed DVD players are unable to play back data recorded on the DVD-ROM since they do not have the key for decrypting the encrypted data. In this manner, in the content scrambling system, DVD players that do not satisfy conditions demanded for receiving a license are unable to play back digital data from a DVD-ROM, thereby preventing unauthorized copying.
A management system for content stored in information recording media is constructed, as described above. Another type of system that allows users to easily download content, such as effect sound, moving pictures, and still images, that can serve as materials for video products is disclosed in Japanese Unexamined Patent Application Publication No. 2003-140662. Additionally, a technique for substituting data indicating part of a piece of music with another data is disclosed in Japanese Unexamined Patent Application Publication No. 2002-311967. It is however difficult to implement the secure data management or usage management for data generated by executing programs stored in information recording media by users or data or content obtained from external servers.
To perform the secure management for data generated by executing programs stored in information recording media by users or data obtained from external servers, it is necessary to handle individual data by, for example, setting a password for each data by a user input or by encrypting each data by using a cryptographic key obtained from an external source. In this data management structure, however, if the number of data generated or obtained by users afterwards is increased, the number of cryptographic keys or passwords is also increased. Additionally, the location of data becomes unclear and the correspondence between stored data and the cryptographic keys or passwords also becomes unclear. Sufficient measures have not yet been taken for the usage management for such subsequently generated/obtained data.
In particular, in an environment where various application programs can be run, such as in a PC, generally, directories managed by a general-purpose file system are set, and files generated by the corresponding programs can be accessed from various applications. Accordingly, it is preferable that, as well as normal files, subsequently generated/obtained data that should be managed by the content management system be also set in management directories of the general-purpose file system. In this case, however, if special settings are not made, the subsequently generated/obtained data is accessed from various application programs, which cause the unauthorized use or tampering of the data.
There are various types of subsequently generated/obtained data, such as data used in accordance with content stored in a specific information recording medium, data that can be used in common for content provided by a specific studio, which serves as a content providing entity, and data that can be used in common for content provided by various studios. It is necessary to perform usage control in accordance with the type of subsequently generated/obtained data. In a current system, however, it is difficult to perform usage control in accordance with the type of subsequently generated/obtained data. Japanese Unexamined Patent Application Publication No. 2005-92830 discloses a content usage system in which a certain file is encrypted with a key file different from a unit key used for encrypting content data. The above publication, however, merely discloses that another key is used for encrypting an application execution file without content real data therein, and assigning a key to a certain type content that has to be simultaneously played back with another type of content is not disclosed. Additionally, it can be considered that a virtual file system is constructed for playing back content recorded on a first recording medium, such as an optical disc, and content recorded on a second recording medium, such as a hard disk. In this case, it is desirable that suitable management of the two types of content be performed. The virtual file system is disclosed in, for example, WO2005/050528.